Small oil filter o ring

[Arizoni]

Yah.  A few days ago when I changed my oil and filter I looked for the "small O-ring" and found it under the silver washer.
The silver washer is spring loaded against the O-ring and the only way to get to it is to disassemble the spring loaded cap.
Why anyone would ever want to do that is beyond me.  That O-ring will last 30 years if it is left alone.

I'm pretty sure your gold (brass?) washer is mounted correctly in the photo.
The big O-ring between the washer and the filter sits outside the "bump" on the washer, being almost equal to the outside diameter of the gold washer.

[Ducati Scotty]

Yes, it is mounted correctly.  I was thinking backwards. 

All the I-rings get stiff after a while.  I always check them all and replace as needed.

Scott

[barenekd]

The case seal is another matter!

When I needed a new timing cover gasket,  CMA sent me a tube of sealer. No gasket needed. Get some Permatex Black Gasket Maker. it will work fine, probably than the gasket. Follow the instructions, though, and be careful around some oil passages. They don't like to be clogged.
Bare

[Ducati Scotty]

+1 After having just done the 10K service and popped the right side case off.  I used the paper gasket but next time I'd use Permatex.  It's a big floppy gasket to keep in place while you get it all together, kind of a pain.

Scott